Wounds occur when the integrity of tissue is compromised, affecting one or more layers of the epidermis or underlying tissue. There are several types of wounds, including acute, chronic, and iatrogenic wounds. Acute wounds may be caused by an initiating event, such as a accident-related injury, surgical procedure or by operation of an infectious disease. Acute wounds caused by accident-related injuries generally take the form of punctures, abrasions, cuts, lacerations, or burns. Acute wounds caused by surgical procedures may be in the form of incisions caused by cutting into or through the skin using a scalpel or other sharp instrument. For example, depending on the procedure, an incision may extend through some or all of the layers of the skin, e.g., through the epidermis, dermis and subcutis, as well as into or through muscle, bone, ligaments, and/or internal organs as needed for the surgeon to be able to access the body part to be treated. Chronic wounds are wounds that generally do not heal within three months, due to one or more of ischemia of the vessels supplying the tissue, venous hypertension or compromise of the immune response, such as observed, for example, with venous ulcers, diabetic ulcers and pressure ulcers. Depending on etiology, such as diabetes, venous insufficiency, or cardiovascular failures, acute wounds may become recalcitrant and even chronic. Iatrogenic wounds are wounds that were initially acute and caused by surgical incision, but become infected.
There are three general classes of wound treatment techniques, commonly referred to as “primary intention,” “secondary intention,” and “tertiary intention.” Primary intention may be used to treat acute wounds that are clean, uninfected, and involve little tissue loss, such as surgical incisions. In a primary intention technique, the edges of the wound are brought together and secured, e.g., using sutures, staples, or adhesive strips. Such wounds have a relatively low risk of infection.
Secondary intention may be used to treat acute or chronic wounds in which there may be sufficient loss of tissue and/or of structural integrity, which may have been caused by tissue necrosis or excision, that primary intention would be inappropriate, e.g., that the skin would need to be stretched too far to safely close the wound with sutures or adhesive. In a secondary intention technique, the wound is left open and allowed to close on its own by the reparative process. Exudate may be allowed to drain freely, and granulation tissue allowed to fill the cavity of the wound. Such wounds have a relatively high risk of infection because they may be exposed to the environment and may be slow to heal.
Tertiary intention, which is sometimes also referred to as “delayed primary closure,” may be appropriate to treat acute wounds that are infected or otherwise experiencing complications, e.g., iatrogenic wounds. In a tertiary intention technique, the wound is often left open for a period of time to allow the complication to at least partially resolve, and then closed using primary intention, e.g., sutures, staples, or adhesive. For example, temporarily leaving such a wound open may allow edema (swelling) or infection to resolve, exudate to drain from the wound, the wound edges to contract, and/or granulation tissue to form. Such wounds may be associated with a high risk of infection and a large loss of tissue.
Conventional wound treatment also typically involves covering the wound with a dressing to prevent further contamination and infection, to retain moisture, and to absorb fluids such as blood or exudate. While exudate contains biochemical compounds that benefit wound healing, excessive exudate in the wound or in the region surrounding the wound, called the “periwound region,” may facilitate degradation of tissue and/or serve as a growth medium for bacteria. For patients with acute wounds and otherwise healthy skin, the presence of excess fluid such as exudate is not a significant concern. However, for patients with chronic wounds, the presence of excess fluid, particularly excess exudate, may delay healing and further damage the skin in the periwound region.
Conventional wound dressings also typically do not address the pain created by the wound treatment system, particularly where the wound treatment system continuously contacts the wound. For example, gauze, which is applied directly onto a wound, is capable of absorbing only a limited amount of exudate, and readily transports excess exudate onto the periwound region, which may cause maceration and damage. Moreover, gauze typically is placed in direct contact with, and adheres to the wound bed, so that normal motion of the patient results in rubbing, itching and discomfort. In addition, removal of the gauze at periodic intervals may be painful and may disrupt at least some of the healing that may have occurred.
Wounds covered with conventional dressings, such as gauze, are also vulnerable to “dehiscence,” or unintentional reopening of the wound. Dehiscence may be caused by physical trauma to the wound and/or by poor wound healing. For example, an incision treated using primary intention, e.g., that is sutured and covered with gauze, may inadvertently be opened if skin on one side of the incision is pulled away from skin on the other side of the incision. Although the sutures may resist such lateral forces, the wound may at least partially open, disrupting some of the healing that may have occurred. The skin may also tear in the vicinity of the sutures, depending on the magnitude of the force. Wounds treated by secondary or tertiary intention may be at least as vulnerable to dehiscence as those treated by primary intention, because they not only lack sutures for resisting such lateral forces, but also may have worse structural integrity because of poor skin health in the region of the wound. Poor wound healing also can increase the risk of dehiscence. For example, patients with poor circulation, e.g., diabetics, may have low blood supply in certain parts of their body which may delay wound healing. Some patients may have genetic disorders, diseases, or may take medications that suppress the formation of collagen and/or other tissues needed for healing. Additionally, the longer it takes a wound to heal, the longer the time over which the wound is vulnerable to reopening by physical trauma, which can further delay healing.
Conventional dressings, such as gauze, do not adequately resist lateral physical forces that may cause wound dehiscence, and do not adequately manage fluid that may drain from the wound, among other shortcomings. For example, U.S. Pat. No. 5,060,662 to Farnsworth discloses a bandage including a ring of pliant material, such as a flexible foam, which is disclosed as holding the rest of the bandage out of contact with the wound. Farnsworth discloses that the bandage further includes an air permeable member, fabricated of a material such as nylon gauze, which is affixed to the upper side of the ring; and an outer protective layer, having a plurality of relatively large openings, which is affixed to the air permeable member. Although Farnsworth discloses that the ring, air permeable layer, and protective layer are formed with lines of perforations permitting the bandage to be separated into sections for application to wounds of different sizes, the separate pieces do not interlock with one another when applied around the wound. The separate pieces are therefore susceptible to being separated by lateral forces and, as such, would not adequately resist those lateral forces to protect the wound from dehiscence.
U.S. Pat. No. 6,570,050 to Augustine et al. discloses a bandage for autolytic wound debridement that includes a fluid-impermeable enclosure including a fluid-absorbent material that is positioned to receive and retain exuded fluid that originates in the wound. Augustine discloses that when the enclosure is attached to the skin it creates a closed chamber over the wound, that maintains a near-100% humid atmosphere about the wound. Augustine teaches that such high humidity is desirable, but failed to recognize that collecting exuded fluid in such a chamber may macerate and damage the skin under the chamber. Moreover, the fluid-impermeable enclosure may create a ring of pressure where it contacts the skin, which may not only damage that skin but may actually enhance dehiscence of the wound. Additionally, the bandage of Augustine is not adjustable, and so can only be used with wounds having a narrow range of sizes.
U.S. Pat. No. 7,193,454 to Rosenberg discloses an occlusive dressing system that includes an endless, elongated, flexible, adhesive barrier adapted to be arranged around a wound, and an impermeable sealing film adapted to overlie the barrier and to seal the wound from the environment. Like Augustine, Rosenberg failed to recognize that such a sealed environment may macerate and damage the skin. Additionally, the flexible barrier would provide little resistance to lateral forces, and thus little protection against wound dehiscence, and the impermeable sealing film would not cushion the wound against forces applied from above the wound.
Thus, what is needed is a dressing that resists lateral physical forces that may cause wound dehiscence, that cushions the wound, and manages fluid that may drain from the wound, among other shortcomings.